Does this sound okay?

First of all, you're very limited on space, since it's only about 7.4 us gallons

the pepper cory's are absolutely fine you can put 3 of them in there with no problem

as for the gravel, no problem with the cory's, i have only gravel in my tanks

I would go for either 6 pearl or 6 zebra danios

you could then add 6 rasboras (there are also different color variations out there)

To this set you could easily add a betta if you like them

Hope that helps

Good luck

EB

Increase the shoal numbers so that you have 6 of each kind,this is really the minimum for shoaling fishes like the ones you want to maintain.

Here's how to monitor your cycle, first look for ammonia,it will reach a peak at about 3 weeks,then it will begin to decrease,now look for Nitrites (the bacteria that eat ammonia produce Nitrites, and they are as toxic as ammonia) then watch for the Nitrites to peak,and begin to decline. When the ammonia and Nitrite numbers go to zero,you have a cycled tank. Don't add all of the fish at once. Add one species(start with the catfish,6 of them) and wait for about 2 weeks so the bacteria can adjust to the new bio-load. Then add another shoal(say 6 Zebras for instance), wait another 2 weeks and add the last group. During this time you should be learning how to do your weekly 20% water changes.

Also, if you want to have some fish that occupy the very top of the water column look into some of the Hatchetfishes (either Marbled or Silvers) they are a little more challenging for new fish-keepers,but quite attractive. These surface dwellers are great jumpers,and need a tightly covered and secure tank. Their dietary requirements require a little research,too. But they can offer a lot in the way of interest at the top of the tank, where most fishes don't spend much time.

To make sure about your cycle,look at some of the "fish-less cycle" websites.

id reccomend id reccomend that you get 5 pygmy coires, 5 cardinal tetras, and thats is. with such a small tank, your options are quite limited.